1. Field of the Invention
The present invention relates to movable body drive systems, pattern formation apparatuses, exposure apparatuses and exposure methods, and device manufacturing methods, and more particularly to a movable body drive system that measures the position of a movable body using an encoder system and drives the movable body substantially along a predetermined plane, a pattern formation apparatus equipped with the movable body drive system, an exposure apparatus equipped with the movable body drive system and the exposure method using the movable body drive system, and a device manufacturing method using the exposure apparatus or the exposure method.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing microdevices (electron devices) such as semiconductor devices and liquid crystal display devices, an exposure apparatus such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper) or a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) is mainly used.
In this type of exposure apparatus, in general, position measurement of a stage that holds a wafer, for example, was performed using a laser interferometer. However, a level of required performance has become higher due to finer patterns accompanying higher integration of semiconductor devices. For example, a permissible value of a total overlay error becomes an order of several nm, and according to this permissible value, a permissible value of a position control error of the stage becomes less than or equal to a subnano order. Accordingly, short-term variation of measurement values caused by air fluctuations that is generated due to temperature variation and/or temperature gradient of an atmosphere in a beam path of the laser interferometer cannot be ignored any more.
Therefore, recently, an encoder having a high resolution that is hardly affected by air fluctuations compared with the interferometer has been gathering attention, and an exposure apparatus that uses the encoder for position measurement of a wafer stage or the like is proposed (e.g. refer to U.S. Patent Application Publication No. 2006/0227309, and the like). In the case of an exposure apparatus described in the U.S. Patent Application Publication described above, a grid plate is used, which is located above a substrate table and covers a wide range of an area including an entire area of a movement range of the substrate table.
However, since it is difficult to manufacture the grid plate with a large area and high precision as is disclosed in the U.S. Patent Application Publication described above, a plurality of grid plates needed to be placed side by side. Fighter, to use the grid plate having a large area as is disclosed in the U.S. Patent Application Publication described above has drawbacks in terms of layout and accuracy, and also is almost unrealistic especially in terms of cost.